gsd behavior

Question
Hi I have a gsd who is 15 months old . Every time we meet an other dog on the field ( which he goes on three times a day) he is very aggressive and wants to fight with other dogs . We have kept him on his lead until he has sniffed the other dogs and then he seems ok. It`s the initial meeting that is bad. Also he does`nt really like meeting stangers on the field , he thinks they have all got dogs with them . On our own with no other animals around he is fantastic , sits, stays come on command , no snatching or aggression towards any one in the family at all. Can yoy please advise me on how to deal with him on the field , it is a shame because i am getting to a stage were i hate meeting another dog whilst out walking !!
Please help !!
Kind Regards Julie

Answer
If your dog is not neutered, do it asap.  Additionally, you are most likely seriously contributing to this behavior.  What you perceive as "aggessive and wants to fight" is most likely NOT that at all.  You are misreading his body language.  If he truly wanted to 'fight' sniffing the other dog would not extinguish that behavior.  You are most likely seeing a normal GSD male presenting with (perhaps) dominant, but most likely insecure, body language toward other (most likely male) dogs and your contribution to this behavior is exacerbating his reaction to them.  You need to find a certified applied animal behavior expert who can observe the actual proceedings, interpret them accurately for you, and help you deal with your dog's generalization of anxiety response.  He is quickly learning that the object of his anxiety...which you have helped to create -- (meaning, the approach of other dogs) is accompanied by other humans.  If you're in Britain, contact the Association of Pet Behavior Counselors.  If you're in the US, call a veterinary school in your geographical area and find a Ph.D. who will come to your home, take a full history of your dog (including veterinary) and go out to the field with you so s/he can observe this behavior.  I've seen many (MANY!)  GSDs with so called "aggression" problems which were not at all related to dominance or aggression and almost every single one was the result of inappropriate owner perception and handling.